1. Field
The present disclosure relates generally to neutron detection and, in particular, to a method and apparatus for detecting a concentrated source of neutrons.
2. Background
Neutron detection is detecting neutrons entering a detector. Detectors may be of the Geiger-Müller counter, scintillation counter and semiconductor detector.
A Geiger-Müller counter consists of a Geiger-Müller tube and a counting circuit which counts the number of current pulses generated in the tube versus time. To detect neutrons, the tube is filled will a low pressure inert gas such as helium 3 that reacts with neutrons and produces ionizing radiation. Ionizing radiation consists of subatomic particles or electromagnetic waves that are energetic enough to detach electrons from atoms or molecules, ionizing them. Ionizing radiation comes from radioactive materials. The walls and center conductor of the tube are metal with the center conductor charged to several hundreds of volts. The electrons and ions generated by neutron reactions with the gas are collected by walls or center conductors of the tube and appear as a current pulse on the center conductor that is recorded by the counting circuit.
A scintillation counter measures ionizing radiation through the production of light as the scintillation material excited by the ionizing radiation returns to its ground state. When a charged particle strikes a scintillator, this flash of light is produced, which may or may not be in the visible region of the spectrum. Each charged particle produces a flash amplitude that is proportional to the energy of the charged particle. If a flash is produced in a visible region, it can be observed through a microscope and counted by a photomultiplier tube. The association of a scintillator and photomultiplier tube with the counter circuits forms the basis of the scintillation counter apparatus.
Another type of detector is a semiconductor detector. In these detectors, radiation is measured by means of the number of charge carriers set free in the detector which is arranged between two electrodes. Ionizing radiation produces free electrons and holes. The number of electron-hole pairs is proportional to the energy transmitted by the radiation to the semiconductor. Under the influence of an electric field, electrons and holes travel to the electrodes resulting in a pulse that can be measured in an outer circuit. The holes travel in the opposite direction and can also be measured. As the amount of energy required to create an electron-hole pair is known, and is independent of the energy of the incident radiation, measuring the number of electron-hole pairs allows the energy of the incident radiation to be found.
Accordingly, it would be advantageous to have a method and apparatus, which takes into account one or more of the issues discussed above as well as possibly other issues.